Iraqi officials say insurgent attacks around the country have killed at least 20 people, including nine in a car bomb blast in Baghdad.

The car bomb exploded in central Baghdad's Karrada district Sunday as a convoy carrying an Iraqi finance ministry official passed by. At least 20 people were wounded, while the official escaped unhurt.

Elsewhere, the U.S. military says three American soldiers were killed by a suicide bomber in the town of Baquba. Earlier, Iraqi officials reported that a roadside bomb went off near a playground in the city, killing three children. It is unclear if the reports are connected.

In other attacks, a car bomb killed two people in the northern city of Mosul, while a roadside bomb killed a policeman in the central town of Tikrit.

The U.S. military said today that overall insurgent attacks in Iraq have fallen 55 percent since the U.S. fully deployed troop reinforcements to the country in June.

U.S. military spokesman, Rear Admiral Gregory Smith also says Iraqi civilian casualties are down 60 percent across Iraq and 75 percent in Baghdad over the same period.

U.S. Embassy official in Baghdad, Philip Reeker says it is unclear what role Iran may have had in the reduction of violence in Iraq.

The U.S. military says Tehran continues to be what it calls the "principal supplier" of weapons, training and funding to insurgent groups. Iran denies the accusations.